Conventionally, as shown in PTL 1, there is known a valve timing control apparatus including a driving-side rotary body (“a rotation transmitting member” in the document), a driven-side rotary body (“a rotary member” in the document), a fluid pressure chamber formed by the driving-side rotary body and the driven-side rotary body and partitioned into a retard angle chamber and an advance angle chamber by a partitioning portion (“a vane” in the document) provided in the driven-side rotary body, and a fluid control mechanism (“a control valve” in the document) for controlling feeding of the working fluid from a working fluid pump (“an oil pump” in the document) for feeding working fluid and controlling also discharging of the working fluid from the fluid pressure chamber.
The invention described in PTL 1 further includes a first relative rotation restricting means for restricting relative rotational phase of the driven-side rotary body relative to the driving-side rotary body to a range from a most retarded angle phase to a predetermined phase between the most retarded angle phase and a most advanced angle phase and a second relative rotation restricting means for restricting the relative rotational phase from the most advanced angle phase to the predetermined phase. The first relative rotation restricting means includes a first lock pin provided on the side of the driving-side rotary body and a first restricting groove formed in the driven-side rotary body and having a predetermined width along the relative rotation direction. In operation, when the first lock pin protrudes into the first restricting groove, the relative rotational phase can be restricted within the range from the most retarded angle phase to the predetermined phase. Further, similarly to the above, the second relative rotation restricting means too includes a second lock pin and a second restricting groove. In operation, when the second lock pin protrudes into the second restricting groove, the relative rotational phase can be restricted within the range from the most advanced angle phase to the predetermined phase.
In association with feeding of working fluid into the fluid pressure chamber, the working fluid is fed also into the first restricting groove and the second restricting groove, whereby the first lock pin and the second lock pin are respectively retracted from the first restricting groove and the second restricting groove. On the other hand, when the engine is stopped and the working fluid is discharged from the first restricting groove and the second restricting groove, the first lock pin and the second lock pin both protrude into the first restricting groove and the second restricting groove. Namely, the relative rotational phase is restrained to the predetermined phase.
With this arrangement, the engine can be restarted with the relative rotational phase being restrained to the predetermined phase in a reliable manner. Therefore, with setting of the predetermined phase to a desired phase, the relationship between the air intake timing and the ignition timing can be optimized, thereby to improve the starting performance of the engine. For instance, it is possible to obtain an engine with low emission of harmful combustion exhaust product such as hydrocarbon (HC).
Incidentally, with hybrid vehicles which recently attract increasing attention, in order to alleviate the shock (transfer shock) at the time of switchover from a traveling operation using a motor to a traveling operation using an internal combustion engine, an arrangement is sometimes made such that at the time of startup from the stopped condition of the internal combustion engine, the relative rotational phase is set to a phase capable of delayed closing of the intake valve (this phase will be referred to as “a decompression phase” hereinafter), thereby to decompress the inside of the combustion chamber (decompression). However, even when the internal combustion engine is stopped at this decompression phase, it is sometimes difficult to maintain the relative rotational phase to the decompression phase due to torque variation at the time of startup of the internal combustion engine. Then, if a predetermined phase is set to the decompression phase, it is possible to maintain the relative rotational phase to the decompression phase reliably, thereby to improve the reliability in alleviation of the transfer shock.
Meanwhile, normally, during an engine operation, displacement forces in the retard angle direction and the advance angle direction due to torque variations of the camshaft are applied to the drive-side rotary body. When averaged, the resultant displacement force is effective in the retard angle direction, so that the driven-side rotary body tends to be displaced in the retard angle direction. In the following discussion, the averaged displacement force of the displacement forces in the retard angle direction and the advance angle direction due to torque variations of the camshaft will be referred to as “the averaged displacement force in the retard angle direction based on torque variations of the camshaft”. In the case of the valve timing control apparatus described in PTL 1, by provision of a torsion spring for applying torque in the advance angle direction to the driven-side rotary body, it is made possible to displace the relative rotational phase in the advance angle direction in a smooth and speedy manner, in spite of the averaged displacement force in the retard angle direction based on torque variations of the camshaft.